Paper bulking promoter

ABSTRACT

According to the present invention, a bulky sheet can be obtained without reducing the effect of a sizing agent. Thus, an ester compound having the melting point of not more than 100° C. selected from (A) an ester compound of a polyhydric alcohol and a fatty acid and (B) an ester compound of a polyhydric alcohol and a fatty acid further including from more than 0 mole to less than 12 moles on the average of C 2-4  oxyalkylene groups per 1 mole of the said ester compound is used as a paper bulking promoter.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP99/02947 which has an Internationalfiling date of Jun. 2, 1999, which designated the United States ofAmerica.

TECHNICAL FIELD

This invention relates to a paper bulking promoter with which sheets ofpaper obtained from a pulp feedstock can be bulky without reducing theeffect of a sizing agent.

BACKGROUND ART

Recently, there is a desire for high-quality paper, e.g., paperexcellent in printability and voluminousness. Since the printability andvoluminousness of paper are closely related to the bulkiness thereof,various attempts have been made to improve bulkiness. However pulprecycling is made to be impossible as well as smoothness of a paper ismade to be impaired. Although a paper bulking promoter containing acertain alcohol and/or a polyoxyalkylene adduct thereof was alsodisclosed (WO98/03730), it may be associated with an insufficiency inexerting the effect of a sizing agent employed generally in combination.Furthermore, a bulking promoter, which is a fatty acid polyamidepolyamine, is an available commercially, but has only a limitedperformance.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a paper bulkingpromoter by which sufficient bulking effect can be obtained even whenthe bulking promoter is added in a small amount and which does furthernot reduce the performance of a sizing agent added in paper-preparingstep.

Thus, the invention provides a paper bulking promoter comprising anester compound having the melting point of not more than 100° C.selected from (A) an ester compound of a polyhydric alcohol and a fattyacid and (B) an ester compound of a polyhydric alcohol and a fatty acidfurther including from more than 0 mole to less than 12 moles on theaverage of C₂₋₄ alkylene oxide (hereinafter referred as OA) groups per 1mole of the said ester compound.

INDUSTRIAL APPLICABILITY

According to the paper bulking promoter of the present invention, anexcellent bulking effect can be obtained even when the paper bulkingpromoter is added in a small amount, and a bulky sheet can be obtainedwithout impairing an effect of a sizing agent.

MODE FOR CARRYING OUT THE INVENTION

An ester compound of the paper bulking promoter in the present inventionis:

(A) an ester compound of a polyhydric alcohol and a fatty acid (an estercompound having no OA group) having the melting point of not more than100° C., or,

(B) an ester compound of a polyhydric alcohol and a fatty acid, furtherincluding from more than 0 mole to less than 12 moles on the average ofC₂₋₄ OA groups per 1 mole of the said ester compound and having themelting point of not more than 100° C.

Both members as (A) and (B) of these esters may be used in combination,and two or more of each member of esters may also be used.

A polyhydric alcohol as a constituent of an ester compound in thepresent invention is preferably a 2- to 14-hydric alcohol having 2 to 24carbon atoms in total which may contain an ether group. A 2-hydric(dihydric) alcohol may be one which has 2 to 10 carbon atoms in totaland which may contain an ether group, such as propylene glycol,dipropylene glycol, butylene glycol, dibutylene glycol, ethylene glycol,diethylene glycol and polyethylene glycol. Then, 3-(tri) or more hydricalcohol may be one which has 3 to 24 carbon atoms in total, which maycontain an ether group and wherein the total number of hydroxy group/thetotal number of carbon atoms=0.4 to 1 in one molecule, such as glycerol,poly(n=2 to 5)glycerol, pentaerythritol, dipentaerythritol, arabitol,sorbitol, stachyose, erythrite, arabite, mannite, glucose and sucrose.Preferably, there are ethylene glycol, diethylene glycol, propyleneglycol, and an alcohol which has 3 to 12 carbon atoms in total, whichmay contain an ether group, wherein the total number of hydroxygroup/the total number of carbon atoms=0.5 to 1 in one molecule, andwhich is 3- or more hydric alcohol. More preferably, there are glycerol,poly (n=2 to 4) glycerol and pentaerythritol.

Further, a fatty acid constituting an ester compound of the presentinvention may be a fatty acid having 1 to 24 carbon atoms, preferably 10to 22 carbon atoms. It may be any one of saturated, unsaturated, linearand branched one. A linear saturated fatty acid is particularlypreferable. More preferably, there are lauric acid, stearic acid,palmitic acid, myristic acid and behenic acid.

The ester compound of the present invention may be obtained by carryingout of conventionally known esterification and adding of alkylene oxide.For example, a mixture of a fatty acid and a polyhydric alcohol is, ifnecessary, admixed with an esterification catalyst and reacted at 150 to250° C. to obtain an ester compound (A), to which an alkylene oxide isadded in the presence of an alkaline catalyst, whereby obtaining analkylene oxide adduct (B). Alternatively, an esterification reaction maybe carried out, after an alkylene oxide is added to a fatty acid or apolyhydric alcohol. Furthermore, it can be sometimes obtained by onlyadding an alkylene oxide to a fatty acid, too.

The average esterification degree of an ester compound in the presentinvention is more than 0. Preferably, per 1 mole of a polyhydricalcohol, OH in the alcohol has been esterified in an amount of 10 to 95%by equivalent. An alcohol has particularly preferably 1 to 2 moles of afatty acid group per 1 mole of polyhydric alcohol.

When an ester compound (B) containing an OA group having 2 to 4 carbonatoms is used as a paper bulking promoter of the present invention, thenumber thereof (OA group) is on the average from more than 0 to lessthan 12 moles, preferably not more than 6 moles, and actually preferably0.1 to 6 moles, per 1 mole of the ester compound. When a polyhydricalcohol, which can become an OA group, such as ethylene glycol, is used,the mole numbers thereof are also counted as the number of OA groups. AnOA group is formed by adding an alkylene oxide having 2 to 4 carbonatoms. A preferred alkylene oxide is ethylene oxide (EO) or propyleneoxide (PO). These may be used as any one of EO, PO and a mixture of EOand PO. In the present invention, it is particularly preferable to usean ester compound containing no OA group as a paper bulking promoter.

An ester compound of the present invention has HLB of preferably 1 to14, more preferably 1.5 to 10, further preferably 2 to 8. HLB is anindex for the hydrophilicity of a surfactant. The larger the value ofHLB is, the higher the hydrophilicity becomes. In the present invention,the HLB of each compound is calculated by the following formulaaccording to Griffin's method.${HLB}\quad = {\frac{{Molecular}\quad {weight}\quad {of}\quad {hydrophilic}\quad {group}\quad {moiety}}{{Molecular}\quad {weight}\quad {of}\quad {ester}\quad {compound}} \times 20}$

And, in the present invention, a hydrophilic group means the followinggroup in an ester compound.

(1) —(CH₂CH₂O)m—

(2) —(RO)_(n)— [R: alkylene group having 3 to 4 carbon atoms,

n<2.0, wherein n is a total number in one molecule]

For example, the underlined part in RCOO—(PO)₁₋₅H represents ahydrophilic group. On the other hand, the underlined part inRCOO—(PO)₂₋₀H represents a hydrophobic group.

Further, in the case of the following formula:

any PO group is a hydrophobic group since one molecule contains 2 molesof PO in total.

(3) A group derived from an alcohol which may have an ether group, whichis a 3- or more hydric alcohol having 3 to 24 carbon atoms in total, andwherein the total number of hydroxy group/the total number of carbonatoms=0.4 to 1 in one molecule.

(4) An oxygen atom adjacent to a carbonyl group.

An ester compound of the present invention has the melting point of 100°C. or lower, preferably −15° C. or higher and 80° C. or lower, morepreferably 20° C. or higher and 70° C. or lower, from the viewpoint ofhandleability and preserving a sizing performance. The melting point ismade to be a temperature of peak beginning, when a solid ester compoundpre-cooled is measured (temperature raising ratio of 2° C./minute) by adifferential scanning calorimeter (DSC).

An ester compound of the present invention is preferably one having HLBof 2 to 8 and the melting point of 10 to 70° C., and more preferably onehaving HLB of 2 to 7 and the melting point of 45 to 70° C. Within suchrange, more preferable results of the bulk promoting effect and thesizing effect (maintained effect of a sizing agent) can be obtained.

A paper bulking promoter of the present invention is added at any stepof papermaking. When it is a liquid product, it may be added as it is.Then, when it is a solid product, it may be added after pulverizing,fusing by heat or diluting with water etc. Further, if necessary, anonionic, anionic, cationic and polymeric surfactant, and preferably anonionic surfactant, may be used as an emulsifier or dispersant. In suchcase, the ratio of a paper bulking promoter in the present invention anda surfactant is: [a paper bulking promoter of the presentinvention]/surfactant=99.5/0.5 to 70/30 (by weight), preferably 98/2 to80/20.

The bulking promoter of the present invention is applicable to a varietyof ordinary pulp feedstocks ranging from virgin pulps such as mechanicalpulps including TMP (thermomechanical pulp) and chemical pulps includingLBKP (bleached hardwood pulp) to pulps prepared from various wastepapers. The point where the bulking promoter of the present invention isadded is not particularly limited as long as it is within thepapermaking step. The papermaking step is to form paper layers bydraining water from a diluted liquid of a pulp feedstock throughout theadvance thereof on a wire netting. In a factory, for example, thebulking promoter is desirably added at a point where it can be evenlyblended with a pulp feedstock, such as, refiner, machine chest, orheadbox. After the bulking promoter of this invention is added to a pulpfeedstock, the resultant mixture is subjected as it is to sheet forming.The bulking promoter remains in the paper. The paper bulking promoter ofthis invention is added in an amount of 0.01 to 10% by weight,preferably 0.1 to 5% by weight, based on the pulp feedstock. But, in thecase of some system, an excellent bulking effect can be obtained byadding a small amount of 0.1 to 1% by weight.

The pulp sheet obtained by using the paper bulking promoter of thepresent invention has a bulk density (the measurement method is shown inthe Examples given later) lower by preferably at least 5%, morepreferably at least 7%, than the product not containing the paperbulking promoter.

At the time of papermaking, it is allowable to add a sizing agent suchas a rosin, an alkyl ketene dimer, gelatin, starch and latex, moreover afiller, a yield improver, a drainability improver, a paper strengthimprover, and the like. A sizing agent fills voids on the surface orbulk of the paper with a water-proof material to suppress the permeationof water or inks, and can be used for paper-treatment by adding to apulp slurry (inner sizing) or coating onto a resultant paper (surfacesizing). A sizing agent is added usually in an amount of 0.01 to 1.0% byweight based on a pulp feedstock, although the amount may vary dependingon the types of the paper. Since a paper bulking promoter of the presentinvention is excellent also in preserving a sizing performance, it isapplied preferably to a method for producing an obtainable highly bulkypulp sheet using a sizing agent in combination.

EXAMPLES Examples 1 to 22 and Comparative Examples 1 to 9

[Pulp Feedstock]

The deinked pulp and the virgin pulp shown below were used as pulpfeedstocks.

<Deinked Pulp>

A deinked pulp was obtained in the following manner. To feedstock wastepapers collected in the city (newspaper/leaflet=70/30%) were added warmwater, 1% (based on the feedstock) of sodium hydroxide (based by weight,this is true hereinafter), 3% (based on the feedstock) of sodiumsilicate, 3% (based on the feedstock) of a 30% aqueous hydrogen peroxidesolution, and 0.3% (based on the feedstock) of EO/PO block adduct ofbeef tallow/glycerol (1:1), as a deinking agent, in which the amounts ofEO and PO were respectively 70 and 10 (average number of moles added).The feedstock was brushed out and then subjected to flotation. Theresultant slurry was washed with water and regulated to a concentrationof 1% to prepare a deinked pulp slurry. This had a freeness of 220 ml.

<Virgin Pulp>

A virgin pulp was prepared by brushing out and beating an LBKP (bleachedhardwood pulp) with a beater at room temperature to give a 1% LBKPslurry. This had a freeness of 420 ml.

[Papermaking Method]

Each of the above 1% pulp slurries was weighed out in such an amount asto result in a sheet of paper having a basis weight of 60 g/m². The pHthereof was adjusted to 4.5 with aluminum sulfate. Subsequently, variousbulking promoters shown in Table 1 and 2 were added in amount of 0.8%based on the pulp, besides rosin sizes as sizing agent were added inamount of 0.5% based on the pulp. Each resultant mixture was stirred,and was formed into a sheet with a rectangular TAPPI paper machine usingan 80-mesh wire. The sheet obtained was pressed with a press at 3.5kg/cm² for 2 minutes and dried with a drum dryer at 105° C. for 1minute. After each dried sheet was held the conditions of 20° C. and ahumidity of 65% for 1 day to regulate its moisture content, it wasevaluated for bulk density and sizing degree by the following methods.The found value was an average of 10 measurements. The results are shownin Table 3.

<Evaluation Item and Method>

Bulkiness (Bulk Density)

The basis weight (g/m²) and thickness (mm) of each sheet having aregulated moisture content were measured, and its bulk density (g/cm³)was determined by the following calculation.

Equation for calculation:

Bulkiness (bulk density)=(basis weight)/(thickness)×0.001

The smaller the absolute value of bulk density is, the higher thebulkiness is. A difference of 0.02 in bulk density is sufficientlyrecognized as a significant difference.

Sizing-ability

The sizing performance was evaluated as directed in JIS P 8122-54 usingStöckigt sizing degree determination method. Thus, a 2 cm×2 cm testpiece of a paper obtained after the sheet formation process was floatedon a 2% solution of ammonium thiocyanate at 20±1° C. contained in apetri dish and treated with dropwise addition of a 1% solution of ferricchloride at the same temperature using a pipette, and the time perioduntil three red spots appeared on the test piece was determined as thenumber of seconds, which represented the sizing degree. It isadvantagoues industrially to keep the sizing degree of 80% of that of ablank (Comparative 1) or higher.

TABLE 1 Paper bulking promoter AO type and number AO of of molesaddition Melting Examples Ester compound added form HLB point (° C.) 1Ethylene glycol — — 5.0 −2 monolaurate 2 Stearic acid — — 5.1 66monoglyceride 3 Pentaerythritol — — 6.7 52 monostearate 4 Propyleneglycol — — 3.7 41 sesquipalmitate 5 Sorbitan monomyristate — — 8.7 30 6Arabitol dioleate — — 4.4 25 7 Soribitol trilaurate — — 4.9 11 8Saccharose monooleate — — 11.3 59 9 Ethylene glycol — — 3.2 64monobehenate 10 Diglycerol monomyristate — — 8.8 52 11 Dipentaerythritol— — 6.9 49 dipalmitate 12 Triglycenrol sesquioleate — — 7.8 12 13Tetraglycerol — — 10.8 61 monostearate 14 Ethylene glycol EO 1 mole —5.7 −3 monooleate 15 Lauric acid monoglyceride PO 0.4 mole — 7.7 45 16Pentaerythritol EO 2 moles Block 8.1 18 monomyristate PO 2 moles 17Propylene glycol EO 1.5 moles Random 4.6 13 monopalmitate PO 4 moles 18Sorbitan monolaurate EO 6 moles — 14.0 −4 19 Xylitol monostearate PO 2moles — 5.7 41 EO 6 moles Block 8.4 5 20 Mannitol sesquioleate PO 4moles 21 Diethylene glycol EO 2 moles monodecylate PO 5 moles Random 6.0−1 22 Emulsified product of — — — — Example 3

The molar number of AO (Alkylene Oxide) added is an average number of AOmoles added per 1 mole of an ester compound.

In the case of block addition, addition is conducted with EO and thenwith PO.

(Note) The composition of Example 22 represents a 10% emulsion ofExample 3/Polyoxyethylene (average number of EO moles added: 10)sorbitan monolaurate=95/5 (by weight).

TABLE 2 Paper bulking promoter AO type and number AO of Comparative ofmoles addition Melting Examples Ester compound added form HLB point (°C.) 1 Blank (containing no — — — — bulking promoter) 2 Lauryl alcohol EO3 moles Block 11.0 5 PO 1 mole 3 C₁₂₋₁₃ oxoalcohol EO 1.5 moles — 6.4 −24 80/20 (by weight) — — 4.3 2 mixture of decyl alcohol/30 moles of EOadduct to sorbitan trioleate 5 Sorbitol tetraoleate EO 30 moles — 11.7−10 6 Sorbitan monopalmitate EO 20 moles — 16.3 −14 7 Commercial bulking— — — — promoter “Bayvolume P Liquid” (fatty acid polyamide polyaminetype; manufactured by Bayer AG) 8 Sorbitan monooleate EO 12 moles — 14.5−5 9 Distearyl phthalate — — 1.0 45

The number of AO (Alkylene Oxide) moles added is an average number ofadded moles per 1 mole of monomer ester.

In the case of block addition, addition is conducted with EO, and thenwith PO.

TABLE 3 Deinked pulp LBKP Bulk Sizing Bulk Sizing density degree densitydegree (g/cm³) (second) (g/cm³) (second) Examples 1 0.339 58 0.382 66 20.315 73 0.361 82 3 0.313 72 0.360 82 4 0.327 67 0.372 76 5 0.330 640.376 72 6 0.331 63 0.377 71 7 0.335 61 0.377 67 8 0.326 70 0.369 78 90.318 72 0.362 82 10 0.320 71 0.364 81 11 0.324 69 0.367 78 12 0.336 620.378 67 13 0.317 72 0.363 81 14 0.340 57 0.384 66 15 0.322 69 0.366 7816 0.338 62 0.380 70 17 0.337 62 0.379 69 18 0.344 56 0.388 65 19 0.32868 0.373 76 20 0.339 59 0.383 68 21 0.341 57 0.385 67 22 0.313 71 0.36082 Comparative examples 1 0.376 70 0.413 80 2 0.362 0 0.404 0 3 0.362 90.405 10 4 0.365 0 0.406 0 5 0.367 0 0.407 0 6 0.363 0 0.404 0 7 0.372 00.411 0 8 0.360 8 0.403 10 9 0.373 15 0.412 17

What is claimed is:
 1. A method for producing a highly bulky pulp sheet,said method comprising adding a paper bulking promoter to a pulpfeedstock in a papermaking process in the amount of 0.1 to 10% by weightbased on the pulp feedstock; wherein said paper bulking promotercomprises an ester compound having the melting point of not more than100° C., selected from (A) an ester compound of a polyhydric alcohol anda fatty acid and (B) an ester compound of a polyhydric alcohol and afatty acid further including from more than 0 mole to less than 12 moleson the average of C₂₋₄ oxyalkylene groups per 1 mole of the said estercompound; wherein 10 to 95% by equivalent of OH groups of the alcoholhave been esterified.
 2. A method as claimed in claim 1 wherein a sizingagent is further added to a pulp feedstock in a papermaking process. 3.The method for producing a highly bulky pulp sheet of claim 1, wherein asizing agent and a surfactant are added to said pulp feedstock in thepapermaking process.
 4. The method of claim 1, wherein the fatty acid ofsaid paper bulking promoter has 10 to 22 carbon atoms.
 5. The method ofclaim 1, wherein the ester compound of said paper bulking promoter hasan HLB of 1 to
 14. 6. A highly bulky pulp sheet produced by the methodof claim
 1. 7. The method of claim 1, wherein said paper bulkingpromoter is added to the pulp feedstock in the amount of 0.1 to 1% byweight based on the pulp feedstock.
 8. The method of 1, furthercomprising the steps of forming paper layers by draining water from adiluted liquid of the pulp feedstock, and forming said highly bulky pulpsheet.
 9. The method of 1, further comprising the step of forming asheet, wherein said bulking promoter remains in the paper.
 10. Themethod of 1, wherein said pulp feedstock is deinked pulp or virgin pulp.11. The method of claim 3, wherein said sizing agent is added in theamount of 0.1 to 1.0% by weight based on the pulp feedstock.
 12. Themethod of claim 1, wherein the polyhydric alcohol of said paper bulkingpromoter is a 2- to 14-hydric alcohol having 2 to 24 carbon atoms intotal which may contain an ether group.
 13. The method of claim 1,wherein the fatty acid of said paper bulking promoter is a fatty acidhaving 1 to 24 carbon atoms.
 14. The method of claim 1, wherein theester compound of said paper bulking promoter contains no oxyalkylenegroup.
 15. The method of claim 1, wherein said highly bulky pulp sheetis printable.